docs: def timeFormat(time_from, time_to=None, prefix="", infix=None):
      """
      Format the times time_from and optionally time_to, e.g. 10am
      """
      retval = ""
      if time_from != "" and time_from is not None:
          retval += prefix
          retval += dateformat.time_format(time_from, "fA").lower()
      if time_to != "" and time_to is not None:
          to = format(dateformat.time_format(time_to, "fA").lower())
          if infix is not None:
              retval = "{} {} {}".format(retval, infix, to)
          else:
              retval = _("{fromTime} to {toTime}").format(fromTime=retval,
                                                          toTime=to)
      return retval.strip()